Of course, people are already blaming the government for the magnitude of the disaster. Sure, having large chunks of the national guard in Iraq made it a bit harder to mobilize (although three-quarters of the Louisiana National Guard was at home, from what I've heard). And sure, diverting money from national disaster preparedness to terrorism preparedness probably exacerbated things (especially on the prevention side of the preparedness equation). But if the federal government isn't blameless, neither is the government of Louisiana, nor the government of New Orleans itself. And truth be told, I doubt any of "mistakes" made added up to a whole lot of difference. The very existence of New Orleans put it at risk in a way that wasn't easily preventable. That's not to say that FEMA and other agencies (or the government in general) shouldn't be held accountable for whatever failures they are responsible for, and that they shouldn't learn from their mistakes, but neither are they responsible for spinning up Katrina or the fact that people (and businesses) chose to live so close to the edge.
Of course, other people have blamed global warming. But Hurricanes happen. And catestrophic hurricanes happen; even if they may not have been as frequent or strong as they are now under other conditions, they still happen. New Orleans was a target regardless. And that's not exactly news -- it's vulnerability was quite well known.
Of course, people blaming global warming have resulted in another backlash of sorts from people who prefer to hide their head in the sand and deny that global warming exists, or that "there's not enough information to know one way or the other." That, of course, seems to more or less be the official position of the Bush administration, and one that can be best described as willful ignorance. Within the scientific community, there's no meaningful debate on that topic -- global warming is here. The open question isn't that, but what the effects will be (if the Bush administration had instead said something to the effect that, yes, global warming exists, but there's not much to be done about it -- or that it's not worth the economic pain to do enough to make much of a difference -- I'd respect that position a lot more. Even the governments that signed the Kyoto treaty have de-facto ended up taking that position). The strange thing is that in the scientific community there's a widespread feeling that we're facing possible climatological disaster, and for the most part, no one on the outside is paying a whole lot of attention (at least until now... With the last couple of hurricane seasons, people may start overreacting in the other direction for all I know).
Specifically, in the case of hurricanes in the Atlantic, it's hard to say what effect global warming has had (if, in fact, it's had any significant effect at all). The problem with studying changes in the weather is two-fold -- first, the system is very much non-linear. Small changes can cause large results, and likewise relatively large changes can be dampened or buffered. The other problem is that the noise drowns out the signal -- given all of the other things affecting day-to-day and even year-to-year weather, it's hard to pick out trends. In the case of hurricanes, we've really only got data going back forty or fifty years, and the quality of the data drops off significantly at the beginning of that period.
That said, various scientists have estimated that the strength of the average tropical cyclone has risen by anywhere from half of a category to two-and-a-half categories in the last century. I suspect there's some effect, and I tend to suspect it's at the lower end of that scale, but there's just not enough data to really tell for sure. Maybe I'll crunch some numbers and generate a few graphs at some point, but I doubt there's anything conclusive to be seen there -- too much noise.
That said, I'm going to make a prediction. I think that in the next decade, we're going to see the amount of greenhouse gases level off, and begin to decline after that.
The reason for that lies in the other part of the unfolding story of the disaster in New Orleans, and that is, of course, oil. For the rest of the summer (and probably for a while after), we're going to be paying for the loss in production (and more importantly, the loss in refining capacity) resulting from Katrina. Of course, that's going to have a short-term effect, but the real reason is because global oil production looks like it's starting to decline (and if not now, then soon). If that's the case, then gas prices are going to start climbing. Or rather, keep climbing. This, of course, has gotten a lot of people worried to the point of terror (a google search for "peak oil" might give you an idea). My old housemate, on the other hand, takes a different view. We've talked about it at length a few times, and I think that in the long-term, he's right... But.
His point is that we can get all the oil we need -- but not at under $3/gallon. Probably the most practical idea right now is to switch to diesel (or, preferably, diesel-hybrid) engines and burn vegetable oil. The main reason we use petroleum is because producing it is essentially free -- you just pull it out of the ground. What you're paying for is transportation, refining, and so forth. And the main reason we haven't switched to alternative fuels (like, say, soybean oil or ethanol) is because they just aren't yet economically competitive. However, at somewhere around $3/gallon, that changes. The real question, though, is how painful the transition will be, whether we're looking at a "shock" or a more gradual transition. I tend to think this is going to take several years of pain to happen, he thinks gas will never get significanly over $3/gallon (we've actually got a bet going on this point).
The primary reason for the current spike in prices at the pump is the loss of refining capacity due to Katrina. We've actually had a bit of refining crunch already, but oil companies haven't been building much in the way of refining capacity lately. Now, they aren't stupid. If they thought they would make money off of refineries, they'd be building them, but they aren't. Under normal (or historical) market growth conditions, it'd certainly be worth it, but they can see the writing on the wall as well as anyone else, and they probably expect that there's going to be a refining overcapacity in the relatively near future.
But to tie this back into global warming by way of greenhouse gases... If we're looking at a switch from petroleum to biologically produced fuels, you've not only got a much more sustainable system, you've also got a system that isn't a net producer of carbon dioxide, since the carbon dioxide that's being produced when you burn the fuel already got pulled out of the atmosphere. Not only that, but an economy that's no longer dependent on imported fuel is a much healthier economy. With the added bonus of not needing to get involved in a fundimentally dysfunctional and violent middle east, something that's probably better for everyone (except maybe them).
Of course, I'm not completely sold yet. One thing I'm wondering about is exactly how much acreage it would take to replace the current rate of petroleum consumption in the US... I'll have to do a bit of research there.